1. Technical Field
The subject matter described here generally relates to wind turbines, and, more particularly, to wind turbine cable twist prevention.
2. Related Art
A wind turbine is a machine for converting the kinetic energy in wind into mechanical energy. If the mechanical energy is used directly by the machinery, such as to pump water or to grind wheat, then the wind turbine may be referred to as a windmill. Similarly, if the mechanical energy is converted to electricity, then the machine may also be referred to as a wind generator or wind power plant.
Wind turbines are typically categorized according to the vertical or horizontal axis about which the blades rotate. One so-called horizontal-axis wind generator is schematically illustrated in FIG. 1 and available from General Electric Company. This particular configuration for a wind turbine 2 includes, a tower 4 supporting a nacelle 6 enclosing a drive train 8. The blades 10 are arranged on a hub 9 to form a “rotor” at one end of the drive train 8 outside of the nacelle 6. The rotating blades 10 drive a gearbox 12 connected to an electrical generator 14 at the other end of the drive train 8 arranged inside the nacelle 6 along with a control system 16 that receives input from an anemometer 18. A cable 20 extends from the from the generator 14 for providing power to the electrical grid (not shown).
The anemometer 18 often includes a vane or other device for determining wind direction which the control system 16 then uses to rotate the “bearing” of the nacelle 6 on its vertical “yaw” axis in order to position the blades 10 so that they are facing into the wind. Commonly-assigned U.S. Pat. No. 7,126,236 entitled “Methods and Apparatus for Pitch Control Power Conversion” is partially reproduced in FIG. 2 where the control system 16 (from FIG. 1) includes one or more controllers within control panel 112 for overall system monitoring and control including pitch and speed regulation, high-speed shaft and yaw brake application, yaw and pump motor application, and fault monitoring.
The control system 16 provides control signals to the variable blade pitch drive or actuator 114 to control the pitch of blades 10 (FIG. 1) that drive hub 110. The drive train 8 (FIG. 1) of the wind turbine 2 includes a main rotor shaft 116 (also referred to as a “low speed shaft”) connected to hub 110 and a gear box 12 that, in some configurations, utilizes a dual path geometry to drive a high speed shaft enclosed within gear box. A high speed shaft from the opposite end of the gear box is used to drive a first generator 120. In some configurations, torque is transmitted via a coupling 122. A yaw system is mounted on a flange provided atop the tower 4.
Yaw drive 124 and yaw deck 126 provide a yaw orientation system for the wind turbine. For example, this yaw orientation system may be electrically operated and controlled by the control system 16 in accordance with information received from anemometer 18. In order to determine the position of the nacelle, mechanical switches (not shown) typically count the number of teeth that are engaged between the yaw drive 124 and the yaw deck 126 as the nacelle 6 is rotated. However, those switches are subject to failure where any disruption of the signals from those switched can cause over-twisting of the cable 20.